JOHNS CREEK, GA. — A PGA Tour player’s bag holds 14 golf clubs, some tools with which to clean them, golf balls, golf gloves, perhaps a drink or two, the odd tee or greens repair tool, a towel, maybe a windbreaker and some rain pants. A caddie’s job, it would seem: Carry it.

Yet as 156 players gather here at Atlanta Athletic Club for the 93rd PGA Championship, which begins Thursday, the role their 156 caddies play is more in focus than ever before. Tiger Woods, still his sport’s No. 1 draw, will play his second tournament with longtime friend Bryon Bell on his bag, a fill-in. Steve Williams, who caddied for Woods for a dozen years before he was fired last month, is now working for Adam Scott, who won the Bridgestone Invitational Sunday — a victory about which Williams was so emotional, he described it in an interview afterward as the “best week of my life.”

The entire affair not only shifted the spotlight at the PGA from Woods’s return to major championship golf — he sat out the U.S. and British Opens with leg injuries — but it crystallized a question, both for avid golfers and those unfamiliar with the sport: How important is a caddie, anyway?

“You could really go both ways,” said Phil Mickelson, the winner of four majors. “You could talk about the importance of having a chemistry and having a trust in your club selection and reads as well as personality, and you can talk about the fact that the caddie never hits a shot, either.”

The latter is precisely what rankled some about Williams’s post-victory remarks. “I think if he had mentioned something about Adam, this wouldn’t have been an issue,” world No. 1 Luke Donald said. Asked Wednesday if Williams’s comments surprised him, Woods said simply, “Yeah.” For his part, Williams tried to put the issue to rest Wednesday by posting an apology on his Web site.

“I felt like my emotions poured out and got the better of me,” Williams wrote.

As Woods’s caddie for 13 of his 14 major championships, Williams — a 47-year-old New Zealander who previously worked for Greg Norman and Raymond Floyd — has a unique position in his profession. He is likely more famous than all but a handful of players in the field, an “over-exuberant sort of guy,” according to British Open champion Darren Clarke.

He is not, though, the only caddie to face scrutiny recently. Dustin Johnson, one of the world’s most talented players, fired caddie Bobby Brown earlier this season — even though he had contended twice in majors in 2010 — and replaced him with Joe LaCava, the longtime caddie for Fred Couples. “It’s huge to get along with them because you spend so much time with them,” Johnson said Wednesday. Rory McIlroy won the U.S. Open in June at Congressional, but he has spent time defending caddie J.P. Fitzgerald after some analysts questioned his course management.

“Everybody’s expectations of a caddie are different, what they mean to you and what you feel as if you need from them,” McIlroy said. “To be honest, I like J.P. because I can talk about things other than golf on the golf course in between shots, take my mind off it, which I like.”

There, then, is the difficult part of a caddie’s job. Getting to the course early, walking off yardages, understanding a player’s game — that’s all important. But understanding when to prod and when to joke might be more so.

“Just trying to play that psychologist out there more than anything” said Steve Stricker, who, at No. 5, is the highest-ranked American in the world. “That’s important at times.”

With Woods still searching for a permanent replacement for Williams — “someone who obviously understands the pressure of the game coming down the back nine,” he said last week — Mickelson and his man, Jim “Bones” Mackay, are likely the pairing with the highest profile. They have been together since 1992 and are close friends, but Mickelson believes that’s in part because Mackay’s job is clearly defined.

“I have a deal with ‘Bones’ that says that I value his input, but I ultimately make the decision,” Mickelson said. “If I disagree with him, I’ll probably go with my gut, even if I’m wrong the majority of the time, because I can live with my own decisions. It’s never the place of the player to take his frustration out on the caddie.”

Earlier this summer, Woods made his decision regarding Williams. Only one has won since, and the deterioration of their relationship has put a spotlight on an entire profession.